Newborn screening is a public health program aimed to identify treatable conditions in presymptomatic newborns to avoid mortality, morbidity and disabilities. With the advent of successful treatment and population screening options for an increasing number of lysosomal storage disorders (LSDs), Friedreich Ataxia, Wilson disease and X-adrenoleukodystrophy, inclusion of these conditions into newborn screening programs seems reasonable. However, larger scale, prospective screening studies have been conducted for only a few of these conditions, and such pilot studies were limited to single conditions where one dried blood spot (DBS) sample was required to measure one analyte as opposed to taking advantage of methods that allow for measurement of several disease markers in the same specimen (multiplexing). Accordingly, little is known to date about performance characteristics of the applied screening tests, such as false positive (FPR) and false negative rates (FNR), positive predictive values (PPV) and detection rate. With partial support from NICHD, Mayo Clinic's Biochemical Genetics Laboratory implemented several screening assays for the simultaneous measurement of multiple biomarkers in single DBS specimens for the detection of up to 13 different LSDs, Friedreich Ataxia, Wilson disease and X-adrenoleukodystrophy. Also with support from NICHD, these assays are tested in a prospective comparative effectiveness study to determine the most efficient and effective approach to newborn screening for these conditions.